Prime Group, owner of the 39-story TechnoMart commercial-residential high-rise in Seoul, said 17 middle-aged people were working out to the pop song "The Power" by Snap on July 5 when their movements set the upper floors of the tower shaking for 10 minutes, according to a report from the Korea JoongAng Daily.

“We observed the vibrometer while performing the same kind of aerobic exercise that was performed at the time of the shaking which occurred on July 5. We noticed that the shaking was felt in the upper floors while the exercise was being performed while no other place showed signs of tremor,” Chung Lan, a professor of architectural engineering at Dankook University, told the Korea Times.

“It just happens to be that the vibration cycle caused by Tae Bo collided with the vertical vibration cycle unique to the building,” Chung told the Korea Times. The action amplified the building's vibration and caused the shaking, he said.

Chung was one of six professors from the Architectural Institute of Korea who inspected the building and recreated the Tae Bo exercise.

soundoff(322 Responses)

Don F.

And what would be the effect of an earthquake occuring at the same frequency? Was this building designed by the same designers as the Tacoma Narrows Bridge?

In the 1800's it was a common practice to under-build dance floors such that they would resonate with the step/beat of the dance, giving the dancers a certin lift. Such floors are typically no longer in existance or being buit because they were structurally unsound. Sounds like this may be the case with this particular building.

Typically vertical forces (as folks jumping up and down on a floor) are transfered to the verticle steel columns. If the floor and the column is stiff enough the force is transmitted directly to the ground. If column is not stiff enough, the force on the floor will exhert a torquing at the point of attachment to the column, This will cause the column to vibrate horizonatlly as the floor is first forced downward and then bounces back up. This will cause the column to flex (vibrate in a wave) along its length causing the floors attached to it to resonate with the floor on which the action is taking place.

Bamboo??? oh.. haha...sad attempt at racist humor. Never mind that Korea ranks higher than the US in Information and Communication Technology (http://www.itu.int/newsroom/press_releases/2003/30.html) and has MUCH faster internet and infrastructural (http://www.netindex.com/). Please disregard that South Korea ranks MUCH higher than the US in education (http://www.geographic.org/country_ranks/educational_score_performance_country_ranks_2009_oecd.html). Our national IQ is also MUCH higher than the US national average (http://www.photius.com/rankings/national_iq_scores_country_ranks.html). Oh and did I mention that South Korea out ranks the US in innovative technology (http://graphics.eiu.com/PDF/Cisco_Innovation_Methodology.pdf). What has the US done in the last 25 years?? Everybody has gotten fat and lazy, and now you worry about falling behind to China and the EU and the rest of the world?? Stop eating potato chips and go to law school and invent something or at least start breeding scientists!

James, your comments are in some ways worse than Rachire's. While Rachire's comments can be considered to have a racial undertone or ill attempt at humor, yours are an all out attempt to justify why you hate American's.

To you answer your question what has America done in the last 25 years, that would be keeping Kim Jung il out of your back yard.

OMG...why did you bring up the bamboo joke? Great, now we have some nationalistic "Uri nara" Korean coming out ranting about how great they are! I met a Korean recently who said, "I work for Microsoft in Korea, if you no what that is." "No! Never heard of it!" I replied. Microsoft??? LOL The only intelligent people on this Earth, according to Koreans, are the Koreans themselves.

When the story about the South Korean building being hurriedly abandoned first came out, I pointed out the very real likelhood that it was problem linked to the fact that many if not most buildings in "The West" and its Allies seem to be mined to prevent use by "enemies" from other countries or even the "rank and file" when they admit that "The West" is just being used by the corporately rich solely as an engine to make them money! Evidence is mined buildings is already massive. Gerald Posner, in "Secrets of the Kingdom: The INside Story of Saudi-U.S. Connections", points out that the Saud family has had all the oil drilling and refining facilities in their country rigged to be obliterated at the touch of a button for some time! In Moscow, excavators of the Moskva Hotel found tons of dynamite in the basement, set to explode if the Nazis took the city and wanted to use the hotel for thei officers. And the UK has a whispered tradition of having eveyrthing from airfields to bridges mined with everything from conventional explosive to nuclear devices, should the nation ever be taken. And, face it, the even in Haiti didn't look like an earthwuake! As localized as it was, with only buildings crumbling, but not things like shrines, and a "tape" of the "event" that showed no roads buckling and that jiggled up an down with precise rhythm, rather than uncontrollably aside-to-side, as in all leigitimate quakes! The evnet iN Haiti appears to have been the dynamiting of charges in all the buidings in Paor-Au-Prince. Add, too, that SIDS has symptoms similar to C$ plastic explosive poisoning. And the fact that the Twi Towers would not completely collapse as they did if the fall was normal. They would have pancaked and the tendency of falling material to take the path of least resistance would have much of it flying outwards, meaning the bottom 20 stories or so would have been left standing! There are films of 20 story hotels falling over from earthquakes and floods and toppling as single solid blocks! They should have been stronger than that! Which brings up the issue of the South Korean building. It should have been stronger! But, it can be sggested, to faciliate anniilation from mines placed within their framework, many buildings today seem to be being build so ramshackle they can start vibrating even from a group of people stomping around!

In war people mine their own bridges. At other times, it gets far-fetched, and makes the arguments seem silly. It is a much better argument to trace the relationships between people (such as News World, Fox, Wall Street Journal, etc.) that cause events, which can effectively cause disasters with much less trouble.

And some people are still advocating allowing marijuana to be legal. This is all the evidence you need to make every drug illegal and use the death penalty for first offenders. JulianPenrod is a nutcase. Yikes !

All structures have at least one resonant frequency that like a capacitor will store energy within the structure and collect the energy over time if the energy (dancing earthquake etc.) continues to be injected into the structure. When designed by engineers structures (guitars pianos buildings) are designed knowing that it is easier to store energy at certain frequencies. Steering the resonant frequency AWAY from earthquake frequencies is the main design goal of building designers in say Tokyo. Not all frequencies of vibration produces the same result in different structures.

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